Adds recursive serialization of boilerplate JSObjects. It also hooks up
serialization of FixedArrays (shallow copy of all elements).

Bug: v8:7790
Change-Id: I458133961918617ab7bdae8d14712a4e5a7d9cb5
Reviewed-on: https://chromium-review.googlesource.com/1188903Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55475}